A Paraconformity and a Record!

A Paraconformity and a Record!

We’ve had a very eventful few days on the JR – geologically speaking! We’ve set a record (another one!) and we’ve hit our target for this drilling site.

We’ll talk about the record first, because it came before the paraconformity! When we hit 1800 meters below sea floor, this hole became the deepest sedimentary rock hole cored on a DSDP, ODP, or IODP expedition. It’s a pretty amazing feat that our drillers have pulled off, drilling that far in sedimentary rock in relatively shallow (for the JR) water. Here is a picture of our record breaking core!

At this depth of 1800 m, we still weren’t seeing evidence of hitting our target, the Marshall Paraconformity. A paraconformity can be difficult to recognize. It is a place in the rock where there is a gap in the rock record – basically missing layers = missing time. What makes a paraconformity different than a disconformity is that the rock layers above and below it are oriented the same. The layers are all laid in the same direction, so there is no immediate visual clue that something has happened in the rock record. In our case, there is a layer of limestone rubble that indicates the paraconformity. While I was off shift yesterday, snoozing away, we hit this paraconformity at a depth of about 1860 meters below sea floor. Here is the accomplishment marked out by the red MP on the core tracking board in the core lab:

Above the paraconformity is a formation called the Otekaike Limestone and below it is the Amuri Limestone. The Amuri limestone is very white and chalky. You can see some in this picture on the right side – see how much lighter in color it is than the other pictures I’ve shown so far?

Dr. Helen Lever can be seen above telling us about the paraconformity and giving Kristen some ideas on where she can see it exposed on land during her time in New Zealand. Below we’ve got Dr. Lever pointing to the actual location where the paraconformity is represented in the core, and also a shot of our liner label!

It’s been amazing to be a part of events that will become a part of IODP history!